A DNS, an abbreviation of Domain Name System, is a core service of Internet. As a distributed database that can mutually map a domain name with IP address, the DNS can make it more convenient for a user to access to Internet without bearing in mind IP strings that can be read directly by a machine.
Usually, an Internet host domain name has a general structure as follows: host name. third-level domain name. second-level domain name. top-level domain name. The top-level domain name of Internet is registered and searched by an Internet network association, and is enrolled and managed by a committee responsible for network address allocation. A unique IP address is allocated for each host on the Internet.
FIG. 1 is a hierarchical architecture diagram of DNS in the prior art. The existing DNS architecture is a hierarchical tree structure which is referred to as a DNS domain name space. An uppermost domain name space is referred to as “root node”. A path from a top-level domain to a sub-domain forms a domain name. For example, a path from a top-level domain.com to its second-level domain Microsoft and then to a sub-domain departmentA of Microsoft forms a domain name of departmentA.microsoft.com.
Wherein, the DNS root server is the “root” of the DNS tree-based domain name space, which is responsible for the resolution of DNS, and plays an extremely crucial role in the domain name resolution. Theoretically, for any form of standard domain name to implement to be resolved, according to the technical process, it must go through the work of the global “hierarchy-type” of domain name resolution system to accomplish.
The first level of the “hierarchy-type” of domain name resolution system is the root server, which is responsible for the management of the domain name information of all countries in the world; and below the root server there is the top-level domain name server, namely, the database of the domain name administration agencies of the relevant country, such as Chinese CNNIC; and then the cache server of the next level of the domain name database and ISP (Internet Service Provider) is turned to for query. A domain name must first pass through the resolution of the root database, then it may be switched to the top-level domain name server for resolution. If the DNS root node cannot be accessed, then all of the domain name resolutions will fail.